A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and so on. Communication systems providing wireless communication for user equipment are known. Cellular communication systems are configured to have a cell structure, and typically they support communication with user equipment changing locations (mobile users). The support for communications for mobile users may include support for handing existing connections from one cell to another cell. At least routing of calls or communications for a mobile user in a new cell is typically supported in cellular systems. Some examples of a cellular system are the Global System for Mobile Telecommunications (GSM) and General Packet Radio Service (GPRS).
Packet-switched networks are those in which relatively small units of data called packets are routed through the network based on a destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network. GPRS provides packet-switched data services and utilizes the infrastructure of a GSM network.
A cellular network is a radio network of individual cells, known as base stations. Each base station covers a small geographical area, and is uniquely identified by a location area code. By integrating the coverage of each of these base stations, a cellular network provides radio coverage over a very much wider area. A group of base stations is called a location area, or a routing area.
A “location area” is a set of base stations that are grouped together to optimise signalling. Typically, 10 s or even 100 s of base stations share a single controller, for example a Base Station Controller (BSC). The controller handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers from base station to base station.
To each location area, a unique number called a “location area code” is assigned. The location area code is broadcast by each base station at regular intervals. A location update procedure allows a mobile device to inform the cellular network, whenever it moves from one area to the next. The user equipment are responsible for detecting location area codes. When a user equipment finds that the location area code is different from its last update, it performs another update by sending to the network, a location update request.
A “routing area” is a subdivision of a “location area”. Routing areas are used by mobiles which are using packet-switched data services. The bursty nature of packet traffic means that more paging messages are expected per mobile, and so it is worth to know the location of the mobile more accurately than it would be with traditional circuit-switched traffic. A change from routing area to routing area (called a “Routing Area Update” (RAU)) is done in an almost identical way to a change from location area to location area. The main difference is that an element such as a “Serving GPRS Support Node” (SGSN) or similar is involved. A RAU procedure thus allows a mobile device to inform the cellular network, whenever it moves from one routing area to the next served by a different SGSN. Mobiles are responsible for detecting routing area codes. When a mobile finds that the routing area code is different from its last update, it performs another update by sending to the network, a RAU request.
A handover minimizes the service interruption times by allowing continuous data transfer between a user equipment and a cellular system when the user equipment is moving from one cell to another cell. A packet-switched handover may be an intra-SGSN handover or an inter-SGSN handover. In an intra-SGSN handover, the source and target base station are controlled by the same SGSN. In an inter-SGSN handover, the source base station is controlled by a first (source) SGSN and the target base station is controlled by a second (target) SGSN.
A GPRS mobile will perform a Routing Area Update in the Ready and Standby state. The RAU is triggered when the mobile crosses a RA (Routing Area) boundary, or periodically with the time interval being set by the network. A RAU is also performed when the mobile moves from the Idle to the Standby state. This will typically happen when the mobile is powered on.
A packet data protocol (PDP) context refers to information sets held in the user equipment and GPRS Supporting Nodes (GSNs) that are used to bind the user equipment to a PDP address that identifies an application, PDP type and a QoS (Quality of Service) profile. That is, the PDP context is a logical association between a user equipment and PDN (Public Data Network) running across a GPRS network. defining aspects such as Routing, QoS, Security, Billing etc. PDP context functions are discussed in 3GPP TS29.060.
Other types of packet switched networks are known. For example, Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. The supporting nodes in this system may be designated 3G-GSNs with the serving support node designated 3G-SGSN. In UMTS, a packet switched signalling connection is a peer-to-peer UMTS connection between the user equipment and 3G-SGSN. It consists of an RRC (Radio Resource Control) connection and an LU connection. In 3G mobile phone technologies, the interface between the access node and a node in the core network is denoted as an LU interface. Over the LU interface, connections can be established according to the LU user plane protocol.
The packet switched signalling connection is needed in UMTS packet domain in order to send signalling messages (e.g. Activate PDP Context Requests) or user data. 3G-SGSN may release the packet switched signalling connection after a GMM (GPRS Mobility Management) specific signalling procedure (e.g. Routing Area Update) or it can prolong the connection for the following activity.
3GPP TS 24.008 describes how the mobile station can request the network to prolong an established packet switched signalling connection using GMM protocol signalling with a follow-on request (FOR) mechanism. If the user equipment wishes to prolong the established packet switched signalling connection, it sets a follow-on request pending indicator (a FOR bit) in a GMM signalling message. If the user equipment does not want to prolong the connection, it doesn't set the follow-on request pending indicator. Networks should prolong the packet switched signalling connection if the mobile station has indicated a follow-on request pending, but they may also prolong the connection without any indication from the mobile station. If a packet switched signalling connection is released, it is re-established with a Service Request procedure.
In current mobile phones the FOR bit is always set if a PDP context(s) is active regardless of whether there is user data transfer ongoing. This means that PS signalling connection might get prolonged without any reason. Thus in current networks the packet switched signalling connection might be prolonged for many hours if the FOR bit is set even if the user data transfer never continues after RAU. This obviously wastes the network resources and also drains out the battery of the user equipment.
On the other hand if the FOR bit is not set, even if there is user data transfer ongoing, the packet switched signalling connection might get released. A user will notice this as a break in the data transfer. The break is caused by the release and re-establishment of the packet switched signalling connection. In the current implementation of the networks this might take several seconds.
The present invention aims to solve the aforementioned problem.